Process for preventing stains on photographic color material during drying following exposure, bleaching, and fixing treatment



Patented Nov; 8, 1949 7 PROCESS FOR PREVENTING STAINS ON PHOTOGRAPHIC COLOR MATERIAL DUR- ING DRYING FOLLOWING EXPOSURE, BLEACHING, AND FIXING TREATMENT Henry B. Kellog, Johnson City, N. Y., assignor to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application December 8, 1945,

Serial No. 633,868

8 Claims. 1

This invention relates to photographic antistain baths, to anti-stain baths employed in multi-color photography, and especially to non-staining baths for the washing of multi-color photographic material following the bleaching treatment.

It is known that in the processing of multicolor reversible film and multi-color reversible film coated upon a white opaque support,. the exposed film or exposed white opaque, is first developed with a normal black and white developer to produce a'negative image. After development, the black and' white negative material,-without being fixed, is exposed to general illumination, followed by a second development with a colorforming developer. During the first and second development the silver-halides in all the layers are reduced to metallic silver. After the second development, the material is cleared in running water, hardened in an aqueous solution consisting of either alum or potassium chrome alum, and then washed in running water. After the latter treatment, the silver present in all the layers formed during the first and second development is converted into a salt by any of the known silver-salt formers, commonly known as bleaching baths, and the silver-salt thus formed is then removed by dissolving it in a silver-salt solvent, such as, for example, hypo. The material is then washed for a long period of time and then dried.

During the washing operation it is essential that the residual second or color developer and bleach solutions be removed, otherwise stains will be formed during the drying operation, which are particularly noticeable in the white area. In order to prevent this staining, an extended final washing time in running water of fromfifteen minutes to two hours, has been proposed. Even if this proposal be adopted, stains are nevertheless formed during and after the drying operation, which makes it imperative to keep the washing time :as short as possible. It is believed that the staining results from the oxidation of traces of the color developer retained in the layers of the material following color-forming development, which then react with the unusedcoler- Other objects and features of the invention will become more apparent as the description proceeds.

I have found that the above objects are accomplished by employing, as a final rinse bath, an aqueous solution containing a small quantity of a substituted or unsubstituted thiourea which corresponds to the following general formula:

tam

wherein R is either hydrogen, methyl or ethyl group, and R1 and R2 which may be alike or different represent hydrogen or an aliphatic hydrocarbon radical of not more than 4 carbon atoms,

e. g., methyl, ethyl, propyl, isopropyl, propenyl, butyl, and the like.

The following are examples of suitable substituted and unsubstituted thioureas which may be employed for the purpose herein set forth.

Thiourea Methylthiourea Ethylthiourea Propylthiourea Z-propenylthiourea Butylthiourea Trimethylthiourea Sym-dimethylthiourea Sym-diethylthiourea Sym-dipropylthiourea Sym-dibutylthiourea As-dimethylthiourea As-diethylthiourea results being obtainable, however, at a concentration ranging from 0.1% to 5%.

The photographic multi-layer materials, which may be processed with the anti-stain bath of the present invention, are color reversible film, color negative film, color reversible white opaque film,

and color paper irrespective of whether the dyestuff images are produced with the color-formers incorporated in the emulsion or by a selective second exposure and color development wherein the color-formers are added to the developing solution. The color reversible film consists of an integral tripack emulsion coated on the usual clear cellulose acetate or nitrate film base. Each of the emulsions are sensitized to one of the primary colors of light; namely, blue, green, and red. The top layer is blue sensitive. A filter layer, yellow in color and blue absorbing, lies under the top layer. Below this filter layer, lies a green sensitive emulsion layer, and below this is a red sensitive emulsion layer. Each of the three silver-halide emulsion layers contain dye-forming compounds which unite during the development of silver image in an aromatic amine developing agent to form a dye with the oxidation product of the developing agent, or may be free from colorformers in which case the film is processed with the color-formers in the color developers by the selective second exposure and color development method as described in United States Patents 1,897,866; 1,900,870; 1,928,709 and 1,980,941. The color negative film is made up in the same manner as the color reversible film, with the exception that it may contain a layer of clear gelatin between the red sensitive layer and the green sensitive layer. The color reversible white opaque material is prepared in the same manner as color reversible film and the color negative film, with the exception 'that the base consists of an opaque while film. The color paper is also constructed in the same manner as the color reversible film and the color negative film, with the exception that the emulsion is coated on a baryta coated paper base.

As silver is formed during development, it must be removed after color development by treatment in a bleach, followed by treatment in a bath of sodium thiosulfate according to usual practice. A yellow dye is formed in the blue sensitive emulsion; a magenta dye is formed in the green sensitive emulsion; and a cyan dye is formed in the red sensitive emulsion. Combinations of these three printing primaries will produce all of the other colors in the finished film or print. Suitable methods for the preparation of photographic multilayer materials have been described in the literature relating to color photography, and are,

therefore, not described here.

The following examples describe in detail methods for accomplishing the above objects, but it is to be understood that they are inserted merely for the purpose of illustration and are not to be construed as limiting the scopeof the invention.

Example I A 4" x 5" full color transparency sheet of color film was printed by contact on two 4" x 5" sheets of color reversible white opaque film.

The two sheets of 4 x 5" color reversible white opaque film were first developed for twelve minutes at 68 F. in a developer of the following composition:

p-Methylaminophenol sulfate grams 3 Sodium sulfite do 50 Hydroquinone do..- 6 Sodium carbonate (monohydrate) do .40 Sodium thiocyanate do 2 Potassium bromide do 2 Water to make up. .liter 1 The developed film was short stopped for 3 minutes at 68 F., in a 5% aqueous solution of sodium bisulfite.

The film was washed for 2 minutes in running water at 68 F., and then color developed for minutes at 68 F., in a developer of the following composition:

p-Aminodiethylaniline HCl grams 4 Sodium sulfite do 5 Hydroxylamine HCI do 2 Sodium carbonate do 40 Potassium bromide do 1 Water to make up liter 1 Di-potassium mono-sodium ferricyanide I grams 100 Potassium bromide do 15 Disodium phosphate do Sodium bisulfate do 25 Formalin (40%) cc 20 Water to make up liter.. 1

. 'The bleached film was washed for 5 minutes at 68 F., and then fixed for 5 minutes in a solution of the following composition:

Hypo ams" 200 Borax do 10 Water to make up liter 1 After fixing, the material was washed for 10-15 minutes in running water at 68 F.

After the final wash, one print was allowed to dry while the other was rinsed in a 0.5% aqueous solution of thiourea and then allowed to dry. At this .point the prints appeared identical. After normal drying, the print rinsed in the thiourea solution showed brighter colors and more brilliant highlights'than the print given only a water wash for 15-20 minutes.

When the drying was carried out under conditions of high humidity so that the drying time was extended for several hours, the water rinsed print showed even greater highlight stains while the print rinsed in the thiourea solution did not change.

Example II Example I was repeated with the exception that the colored material employed was a color paper and the final rinse was a 1% solution of methylthiourea instead of a 0.5% solution of thiourea. The color print washed in water showed objectionable stains after drying while the print treated with the solution containing methylthiourea was clear and unstained.

Example III Example I was repeated with the exception that the final rinse bath was a 1% solution of ethylthiourea instead of a 0.5% solution of thiourea. After fixing and washing, the color print rinsed in plain water showed objectionable stains while the color print treated by a rinsing solution containing ethylthiourea was clear and unstained.

7 From the above examples it is manifest that the 1 multilayer photographic material rinsed in plain water shows marked staining upon drying of said material. This staining occurs especially under slow drying conditions and is probably due to the slow coupling of the oxidation product of the color developer with the residual colorcoupler present in one or more layers.

The above specific examples are to be regarded as merely illustrative of the invention, and not in any sense restrictive. It will be obvious to anyone skilled in the art that many modifications such as substituting equivalent material and varying the proportions of materials used are within the spirit and scope of the invention as defined in the appended claims.

I claim:

1. In a process of color photography, the method of preventing stains on color images selected from the class consisting of indophenol and azomethine dyes produced in a multilayer color film by color-forming development, which comprises rinsing said film after exposure, colorforming development. bleaching, and fixing, with an aqueous solution consisting of water and a compound of the following general formula:

wherein R is a member selected from the class consisting of hydrogen, methyl and ethyl groups, and R1 and R2 are members selected from the class consisting of hydrogen and an aliphatic hydrocarbon radical of not more than 4 carbon atoms.

2. In a process of color photography, the method of preventing stains on color images selected from the class consisting of indophenol and azomethine dyes produced in a multilayer color film by color-forming development which comprises rinsing said film after exposure, color-forming development, bleaching, and fixing, with an aqueous solution consisting of water and thiourea.

3. In a process of color photography, the method of preventing stains on color images selected from the class consisting of indophenol and azomethine dyes produced in a multilayer color film by color-forming development which comprises rinsing said film after exposure, color-forming development, bleaching, and fixing, with an aqueous solution consisting of water and methylthiourea.

4. In a process of color photography, the method of preventing stains on color images selected from the class consisting of indophenol and azomethine dyes produced in a multilayer color film by color-forming development which comprises rinsing said film after'exposure, color-forming development, bleaching, and fixing, with an aqueous solution consisting of water and ethylthiourea.

5. In a process of producing color photographic images selected from the class consisting of indophenol and azomethine dyes in a multilayer color film by exposing the film, color-forming developing the same, bleaching, fixing and washing, the improvement which comprises avoiding the formation of stain, after the aforesaid exposure, color-forming development, bleaching, fixing and washing operation, by rinsing the said film with an aqueous solution consisting of water and a compound of the following general formula:

time

wherein R is a member selected from the class consisting of hydrogen, methyl and ethyl groups, and R1 and R2 are members selected from the class consisting of hydrogen and an aliphatic hydrocarbon radical of not more than 4 carbon atoms.

6. In a process of producing color photographic images selected from the class consisting of indophenol and azomethine dyes in a multilayer color film by exposing the film, color-forming de veloping the same, bleaching, fixing and washing, the improvement which comprises avoiding the formation of stain, after the aforesaid exposure, color-forming development, bleaching, fixing and washing operation, by rinsing the film with an aqueous solution consisting of water and thiourea.

7. In a process of producing color photographic images selected from the class consisting of indophenol and azomethine dyes in a multilayer color film by exposing the film, color-forming developing the same, bleaching, fixing and washing, the improvement which comprises avoiding the formation of stain, after the aforesaid exposure, color-forming development, bleaching, fixing and washing operation, by rinsing the film with an aqueous solution consisting of water and methylthiourea.

8. In a process of producing color photographic images selected from the class consisting of indophenol and azomethine dyes in a multilayer color film by exposing the film, color-forming developing the same, bleaching, fixing and washing, the improvement which comprises avoiding the formation of stain, after the aforesaid exposure, color-forming development, bleaching, fixing and washing operation, by rinsing the film with an aqueous solution consisting of water and ethylthiourea.

HENRY B. KELLOG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,803,906 Krieger May 5, 1931 1,821,281 Van der Grinten Sept. 1, 1931 2,262,055 Sease et a1. Nov. 11, 1941 2,313,138 Frohlich et a1. Mar. 9, 1943 2,384,658 Vittum Sept. 11, 1945 2,397,924 Crabtree et al Apr. 9, 1946 2,440,954 Jennings May 4, 1948 

